Quick and dirty Desert Eagle spotting guide. Doing this from memory, bear with me.
>.357 production prototype circa 1984
These are a 1000 unit production test run to tweak the design before mass production. Smallest or the Deagles. visually the same as later models, but 98% of final production size. Will not accept later caliber conversion kits or barrels. Spotting features, barrel has convention land and groove rifling, serial number is between 3000 and 3999.
>MkI production version, circa 1985.
The frame (lower) will type is finalized and will remain basically the same through subsequent models until the introduction of five inch models on the 2010s. initial version are in .357 Magnum. .44 Magnum version using a slightly larger slide and barrel combo introduced. Spotting features, caliber is on the slide, slide catch is single step, safety levers are "teardrop" style. trigger is non adjustable single stage.
>MkVII introduced circa 1987
.41 Magnum introduced using the same slide and barrel blanks as .44 Magnum. Slide now reads .41/.44 Magnum for .4X caliber guns. .50AE version introduced in 1989. The MkVII .50AE is mechanically identical to the later MkXIX except the MkVII .50AE guns have .50 on the slide instead of the barrel. MkVII spotting features, "hook" shaped safety levers, three step slide release lever, fully adjustable two stage trigger.
>MkXIX circa 1995
All calibers now use .50AE size slide and barrels. .41 Magnum dropped as a caliber. Caliber number (.357, .44, .50AE) moved to barrel gas block. Production moved to Sako Arms during IMI reorganization until 1999. New caliber, .440 Cor Bon, a .50AE case necked down to .44 introduced. Ammo quality control issues lead to .440 barrel production being cancelled with just a thousand or so guns out the door. Production returns to Israel under reorganized IWI and remains in Israel until production is moved to MRIs Pillager, MN plant.